Stratigraphy and Fossil Assemblages of the Upper Cretaceous System in the Makarov Area, Southern Sakhalin, Russian Far East
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The Cretaceous System in the Makarov Area, Southern Sakhalin, Russian Far East, edited by Y. Shigeta and H. Maeda,
National Science Museum Monographs, 31: 25–120, 2005
Stratigraphy and Fossil Assemblages of the Upper Cretaceous System in
the Makarov Area, Southern Sakhalin, Russian Far East
Haruyoshi Maeda1, Yasunari Shigeta2, Allan Gil S. Fernando3 and Hisatake Okada3
1
Department of Geology and Mineralogy, Graduate School of Science, Kyoto University,
Kitashirakawa-Oiwake-cho, Sakyou-ku, Kyoto 606–8502, Japan
E-mail: maeda@kueps.kyoto-u.ac.jp
2
Department of Geology and Paleontology, National Science Museum, 3–23–1
Hyakunin-cho, Shinjuku-ku, Tokyo 169–0073, Japan
E-mail: shigeta@kahaku.go.jp
3
Department of Earth and Planetary Sciences, Graduate School of Science,
Hokkaido University, N10 W8 Kita-ku, Sapporo 060–0810, Japan
E-mail: agsfernando@yahoo.com; oka@ep.sci.hokudai.ac.jp
Abstract The stratigraphy and paleontology of the Cretaceous Yezo Group in the Makarov area has
been thoroughly investigated. Exposures of the group in this area range in age from Santonian to
Maastrichtian, and attain a total thickness of 2,500 m. The group is divided into the Bykov and Kras-
noyarka formations in ascending order. The Bykov Formation consists mostly of offshore mudstones,
and is lithologically subdivided into four lithostratigraphic units designated as B1–B4, while the
Krasnoyarka Formation is composed mainly of nearshore sandstones and deltaic deposits, and is sub-
divided into five units: K1–K4b.
Except for the uppermost part of the Krasnoyarka Formation, the remaining Cretceous strata are
very fossiliferous. Among the fossil fauna, pachydiscid, tetragonitid, and gaudryceratid ammonoids
are especially abundant. Sphenoceramus schmidti, of Middle Campanian age, also occurs frequently,
and forms the characteristic S. schmidti Zone, which is widely traceable throughout the area. It is
noteworthy that a nearly complete faunal succession of Campanian and Maastrichtian age can be con-
tinuously observed even though internationally recognized, stage-diagnostic taxa are few.
The relatively uniform sedimentary features of the mudstone deposits as well as the faunal com-
position of the Yezo Group are similar throughout southern Sakhalin and Hokkaido. Although the
datum planes of a few fossil zones extend across some lithostratigraphic boundaries, almost identical
lithofacies and biofacies extend over 1,200 km in a north to south direction. Such depositional and
faunal uniformity, which reflects the marine environment in the North Pacific during this portion of
Upper Cretaceous time, is a remarkable characteristic of the Yezo Group.
Twenty-five species of ammonoids, distributed among fourteen genera, are described, two of
which, Hypophylloceras (Neophylloceras) victriense and Gaudryceras makarovense, are new species.
Key words: ammonoids, Makarov, Sakhalin, stratigraphy, Upper Cretaceous
tributaries: the Victoria R., the Rechitsa R., the
Introduction
Acacia R., and the Grudzovka R. (Figs. 1, 2).
A continuous succession of the Cretaceous As in the Naiba section, it is worthy of con-
Yezo Group is well exposed along the middle sideration as one of the reference sections for
course of the Makarova River and four of its Cretaceous stratigraphy in Sakhalin. The re-
26 Haruyoshi Maeda et al.
Fig. 1. Map showing the study area in the Makarov area, southern Sakhalin.
gional geology of the area has already been total of 31 samples (001 to 031) (Appendices
outlined, and Cretaceous megafossils have 6, 7; locality maps). Smear slides were pre-
been partly described by previous authors pared from the samples and examined under a
(Sasa & Koiwai, 1960; Vereshchagin 1970, light microscope using both cross-polarized
1977; Salnikova, 1980; Poyarkova 1987; light and phase contrast methods at 1,000
Zonova et al., 1993; Yazikova, 1994 etc.). magnification. In order to determine the rela-
In order to achieve precise stratigraphic cor- tive abundance of species, more than 350
relation between Sakhalin and Hokkaido, a fields of view (FOV) were observed per sam-
Japanese–Russian Joint Research Program ple. Relative abundance categories were adapt-
was begun in 1990 (Kodama et al., 2000, ed from Bown et al. (1998) and Burnett
2002). Scientific expeditions to the Makarov (1998). Additional FOVs were observed to
area were successfully carried out by geolo- check for the presence of rarely occurring, but
gists from both countries in 1993, 1994 and biostratigraphically important species.
1996. Utilizing satellite photography for de- The results of the field survey and laborato-
tailed mapping, we investigated distinctive ry investigations as well as pertinent discus-
sedimentary features of the Cretaceous se- sions are included in this paper.
quence, and carefully observed modes of fossil Repository of specimen: The following ab-
occurrence as well as the biostratigraphy of breviations are used to indicate fossil reposito-
megafossils. ries: NSM, National Science Museum, Tokyo;
In an effort to investigate calcareous nanno- DGMKU, Department of Geology and Miner-
fossil biostratigraphy, we have examined a alogy, Kyoto University, Kyoto. Smear slides
Stratigraphy of the Upper Cretaceous System in the Makarov Area 27 Fig. 2. Satellite photograph of the Makarov area, southern Sakhalin.
28 Haruyoshi Maeda et al.
and original digital images of calcareous nan- Bykov Formation (Vereshchagin, 1961)
nofossils are stored at Hokkaido University. Only the uppermost part of the Bykov For-
All fossils and samples utilized herein were mation is exposed in the Makarov area. It con-
collected during the field expeditions and were sists mainly of monotonous mudstone and is
transported from Russia to Japan with permis- subdivided into lithostratigraphic units desig-
sion from the Russian Government, the State nated as B1–B4.
Government of Sakhalin, and other concerned Stratotype: Naiba area, southern Sakhalin
authorities. (see Matsumoto 1942d, 1954; Zakharov et al.,
1984; Poyarkova, 1987; Kodama et al., 2002).
Geologic setting
B1 Unit
In general, the Cretaceous System dips Exposures: Middle course of the Makaro-
20–45° west, and its strike varies between a va River.
N–S direction and N30°E. It is in fault contact Thickness: Greater than 100 m.
with Neogene volcaniclastic deposits in the Stratigraphic relationship: The basal part
eastern part of the area, and is unconformably is not exposed. The B1 Unit conformably un-
overlain by Paleogene coal measures in the derlies the B2 Unit.
west (see satellite photography). A few diorite Lithology: The B1 Unit consists of dark
sills, extending in a N–S direction, intrude into gray, massive, fine mudstone. Its detailed sedi-
the Cretaceous mudstone (Locs. MK2002, mentological features are uncertain because of
3001, 5003; Fig. 3). At a few localities in the poor exposures.
western part of the area, Cretaceous strata are Megafossils: A few lenticular calcareous
repeatedly exposed by fault displacement and nodules were observed in the mudstone but no
folding. However, such tectonic influences are megafossils were found in the Makarov area.
generally slight, and continuous successions In the Lesnaya area, which is about 8 km south
are easily observable (Appendices 1–8; route of the Makarov area, Damesites sp., Tetrago-
maps). nites glabrus (Jimbo), and Gaudryceras
denseplicatum (Jimbo) occur in calcareous
nodules which are derived from mudstone in
Stratigraphy
the B1 Unit. This ammonoid assemblage is of
In the Makarov area, the Cretaceous System Coniacian or Santonian age.
is stratigraphically equivalent to the Yezo
Group (Supergroup) in Hokkaido, Japan. The B2 Unit
group is generally represented by an extremely Exposures: Loc. MK5002, along the lower
thick clastic marine sequence, which can be course of the Rechitsa River (typical section);
interpreted as having been deposited in a fore- lower course of the Gruzdovka River.
arc basin (Okada, 1979, 1983). Thickness: 20–60 m.
Although only the upper part of the group is Stratigraphic relationship: The B2 Unit
exposed in the Makarov area, it exceeds conformably overlies the B1 Unit, and con-
2,500 m in thickness, and is lithologically sim- formably underlies the B3 Unit.
ilar to sediments of the stratotype section in Lithology: The B2 Unit consists of light
the Naiba area. It is similarly divided into the gray, massive, fine to medium-grained, thickly
Bykov and Krasnoyarka formations in ascend- bedded sandstone. Unlike the sandstones of
ing order. (Figs. 3–6). the Krasnoyarka Formation, the sandstones of
the B2 Unit contain few volcanic fragments.
The unit extends laterally over adjacent
Stratigraphy of the Upper Cretaceous System in the Makarov Area 29 Fig. 3. Geological map of the Makarov area, southern Sakhalin.
30 Haruyoshi Maeda et al. areas. In the Lesnaya area, the sandstones of the B2 Unit coarsen and display slumping structures. The B2 Unit is often intruded by diorite sills. The contact between the diorite and sand- stone is distinct and a thin chilled margin about 1 cm thick, can be observed (Loc. MK2002). Megafossils: No fossils were found in the B2 Unit. B3 Unit Fig. 4. Lithological symbols in columnar sections Exposures: Locs. MK2005–2008 along (Figs. 5, 6, 19). the lower course of the Acacia River (typical section); lower course of the Victoria R. and (Yokoyama) (Fig. 11) is common in the upper Rechitsa R. part, while Eupachydiscus haradai (Jimbo) Thickness: 600 m. and Sphenoceramus orientalis (Sokolov) (Fig. Stratigraphic relationship: At Loc. MK- 16) are abundant in the uppermost part. Usual- 2003 along the Acacia River, the basal part of ly, these pachydiscids are adult macroconchs the unit is in direct contact with an intruded that attain a diameter of 30 cm. diorite sill. At other localities, the B3 Unit In addition, Tetragonites glabrus (Fig. 42) conformably overlies the B2 Unit and con- and Gaudryceras striatum (Jimbo) (Fig. 25) as formably underlies the B4 Unit. well as plant remains are common in the cal- Lithology: The B3 Unit consists mainly of careous nodules in the uppermost part. dark gray, intensely bioturbated, fine mud- stone. Laminations or bedding planes are bare- B4 Unit ly observable in the mudstone. Poorly sorted Exposures: Locs. MK2009–2014 along sandstone beds varying in thickness from 10 the lower course of the Acacia River (typical to 30 cm are occasionally intercalated, and the section); lower course of the Victoria R., Re- thinner beds are usually mottled and penetrat- chitsa R., and Gruzdovka R. ed by burrows. Ellipsoidal calcareous nodules, Thickness: 300–400 m. 30–60 cm diameter, are commonly embedded Stratigraphic relationship: The B4 Unit in the mudstone. conformably overlies the B3 Unit, and con- At Loc. MK2003, mudstone beds adjacent formably underlies the Krasnoyarka Forma- to the contact plane with a diorite sill are horn- tion. felsed. Lithology: The unit consists mainly of Microfossils: Repagulum parvidentatum dark gray, intensely bioturbated, massive or (Deflandre and Fert), Prediscophaera ar- mottled sandy mudstone interbedded with khangelskyi (Reinhardt) and Biscutum mag- white vitric tuff layers that vary in thickness num Wind and Wise occur rarely in the upper from 5–20 cm. Usually, the basal beds are not part of the B3 Unit (Figs. 7, 8; Table 1). exposed, but the more resistant main part Megafossils: Many ammonoids and inoce- of the unit is well exposed. Several shell- ramids are found in ellipsoidal calcareous nod- beds comprised of Sphenoceramus schmidti ules as well as in the host mudstone (Table 2), (Michael) are intercalated in the lower part of but the faunal components change stratigraph- the unit (Loc. MK2009). The S. schmidti icaly within the unit. Menuites naumanni Zone, consisting of such composite type shell-
Stratigraphy of the Upper Cretaceous System in the Makarov Area 31
Fig. 5. Columnar sections of the Cretaceous Yezo Group at four major localities in the Makarov area. Shaded
part in the B4 Unit represents the traceable Sphenoceramus schmidti Zone.
32 Haruyoshi Maeda et al.
Fig. 6. Lithology and faunal succession of the Cretaceous deposits along the Acacia River.
Stratigraphy of the Upper Cretaceous System in the Makarov Area 33
Table 1. List of calcareous nannofossils from the Bykov Formation along the Acacia River. Relative abundance cate-
gories were adopted from Bown et al. (1998) and Burnett (1998). F (few): 1 specimen/2–50 FOV. R (rare): 1
specimen/50 FOV.
B3 Unit B4 Unit
Species
001 002 003 004 005 006 007 008 009 010 011 012 013 014 015
Reinhardtites anthophorus (Deflandre) R R
Reinhardtites levis Prins & Sissingh R
Staurolithites zoensis Burnett R R
Tranolithus orionatus (Reinhardt) R
Zeugrhabdotus praesigmoides Burnett R
Zeugrhabdotus spiralis (Bramlette & Martini) R
Zeugrhabdotus trivectis Bergen R R
Chiastozygus litterarius (Górka) R
Chiastozygus synquadriperforatus Bukry R
Chiastozygus sp. A R
Eiffellithus eximius (Stover) R
Eiffellithus turriseiffelii (Deflandre) R
Helicolithus trabeculatus (Górka) R
Cribrosphaerella ehrenbergii (Arkhangelsky) R
Biscutum coronum Wind & Wise R
Biscutum ellipticum (Górka) R R R
Biscutum magnum Wind & Wise R
Discorhabdus ignotus (Górka) R R R
Prediscophaera arkhangelskyi (Reinhardt) R R
Prediscospaera cretacea (Arkhangelsky) R R
Prediscospaera grandis Perch-Nielsen R
Prediscophaera incohatus (Stover) R
Cyclagelosphaera rotaclypeata Bukry R
Watznaueria barnesae (Black) R R R
Watznaueria spp. R R R R
Arkhangelskiella cymbiformis Vekshina R R
Repagulum parvidentatum (Deflandre & Fert) R R R F F R R R F
Braarudosphaera bigelowii (Gran & Braarud) R
Micula staurophora (Gardet) R R
beds (Ando & Kondo, 1999), attains a thick- (008, 009 and 013) that contain a few Repagu-
ness of 100 m, and is traceable throughout the lum parvidentatum, nannofossil abundance
Makarov area. values are less than 10 specimens per 100
Richly fossiliferous spherical and lenticular FOV.
calcareous nodules, 30–60 cm in diameter, are Megafossils: The entire unit is fossilifer-
common particularly in the upper part of the ous (Table 2). In the lower part, Sphenocera-
unit. mus schmidti (Figs. 17, 18) is abundant in cal-
Microfossils: Reinhardtites anthophorus careous nodules as well as in the surrounding
(Deflandre), R. levis Prins and Sissingh and sandy mudstone. Specimens of S. schmidti,
Arkhangelskiella cymbiformis Vekshina occur 20–50 cm in length, are typically preserved
rarely in the B4 Unit (Figs. 7, 8; Table 1). Cal- with their valves in the closed position, and
careous nannofossil assemblages are few and are embedded horizontally in the intensely
their respective abundance values are general- bioturbated, sandy mudstone. Some specialists
ly very low. Their preservation is poor to mod- argue for taxonomic division of the S. schmidti
erate. With the exception of three samples group (e.g., Michael, 1899; Nagao & Matsu-
34 Haruyoshi Maeda et al.
Fig. 7. Optical micrographs of calcareous nannofossils under cross-polarized light from the B3 and B4 units,
Bykov Formation, along the Acacia River. Scale bar1 m m. 1–3, Arkhangelskiella cymbiformis Vekshina,
sample 013. 4, Biscutum coronum Wind and Wise, sample 008. 5, Braarudosphaera bigelowii (Gran and
Braarud), sample 008. 6, Chiastozygus litterarius (Górka), sample 013. 7, Chiastozygus synquadriperforatus
Bukry, sample 013. 8–9, Chiastozygus sp. A, sample 013, a species of Chiastozygus with a small cross super-
imposed over the symmetrical, central cross. The arms of the smaller cross are approximately half as long and
appear to be parallel to the arms of the larger cross. 10, Cyclagelosphaera rotaclypeata Bukry, sample 005. 11,
Eiffellithus eximius (Stover), sample 005. 12, Helicolithus trabeculatus (Górka), sample 013. 13, Micula stau-
rophora (Gardet), sample 008. 14–15, Prediscosphaera arkhangelskyi (Reinhardt), sample 005. 16, Predis-
cosphaera cretacea (Arkhangelsky), sample 013.Stratigraphy of the Upper Cretaceous System in the Makarov Area 35
Fig. 8. Optical micrographs of calcareous nannofossils under cross-polarized light from the B4 Unit, Bykov For-
mation, along the Acacia River. Scale bar1 m m. 1, Prediscosphaera grandis Perch-Nielsen, sample 013. 2–3,
Reinhardtites anthophorus (Deflandre), sample 013. 4–5, Reinhardtites levis Prins and Sissingh, sample 013.
6–7, Repagulum parvidentatum (Deflandre and Fert), sample 013. 8–9, Staurolithites zoensis Burnett. 8, sam-
ple 013. 9, sample 008. 10, Tranolithus orionatus (Reinhardt), sample 013. 11–12, Watznaueria barnesae
(Black). 11, sample 008. 12, sample 013. 13, Zeugrhabdotus praesigmoides Burnett, sample 008. 14, Zeu-
grhabdotus spiralis (Bramlette and Martini), sample 013. 15–16, Zeugrhabdotus trivectis Bergen, sample 013.36 Haruyoshi Maeda et al.
Table 2. List of ammonids, inoceramids and other invertebrates from the Bykov Formation in the Makarov area.
Species B3 Unit B4 Unit
Ammonoids
Phyllopachyceras ezoense (Yokoyama) 2062 2015
Gaudryceras striatum (Jimbo) 2062
Gaudryceras mamiyai Matsumoto & Miyauchi 2009
Gaudryceras cf. mamiyai Matsumoto & Miyauchi 2015
Anagaudryceras nanum Matsumoto 2062
Tetragonites glabrus (Jimbo) 2062
Tetragonites popetensis Yabe 4004, 2015
Baculites sp. 2015
Damesites cf. sugara (Forbes) 2062
Eupachydiscus haradai (Jimbo) 2062, 4049, 4102
Menuites naumanni (Yokoyama) 2008, 4508, 4515, 5014,
5015, 5020
Canadoceras kossmati Matsumoto 2009, 2010, 2011, 2012, 2014,
2015, 3012, 3013, 4001, 4002,
4003, 4004, 4007, 4008, 4009,
4112, 5035, 5036
Inoceramids
Sphenoceramus nagaoi (Matsumoto & Ueda) 2008
Sphenoceramus orientalis (Sokolov) 2062, 4049, 4101, 4102,
4103
Sphenoceramus schmidti (Michael) 2009, 3003, 3006, 3007, 3008,
3009, 3010, 4000, 4001, 4002,
4003, 4004, 4005, 4006, 4007,
4103, 4104, 4105, 4106, 4107,
4108, 4109, 4110, 4112, 4115,
5026, 5029, 5030, 5033, 5035
Gastropods
Anisomyon cassidarius (Yokoyama) 2008
“Gigantocaplus” transformis (Dundo) 2062, 4102
Gigantocaplus giganteus (Schmidt) 2009, 3003, 4000, 4001, 4005,
4006, 4104, 5026, 5029
moto, 1940; Tanabe, 1973; Zonova et al., 1993 ribbed morphotypes of S. schmidti.
etc.), but we regard S. schmidti as one, highly
variable species. Krasnoyarka Formation (Vereshchagin, 1961)
In the lower part of the S. schmidti Zone, Stratotype: Naiba area, southern Sakhalin
morphotypes occur with diagnostic divergent (see Matsumoto 1942d, 1954; Zakharov et al.,
ribs that are typical for the adult stage. In con- 1984; Poyarkova, 1987; Kodama et al., 2002).
trast, smooth morphotypes, in which divergent The Krasnoyarka Formation consists mainly
ribs appear only in the early growth stage, be- of various types of sandstone as well as sandy
come dominant in the upper part of the zone mudstones, and is divided into four lithostrati-
(discussed later). Canadoceras kossmati Ma- graphic units (K1–K4), which become pro-
tsumoto (Fig. 12) is also abundant in this hori- gressively finer in an ascending sequence ex-
zon. The lowermost shell bed is intercalated in cept for the K4. The formation conformably
predominately sandy matrix and yields Gigan- overlies the Bykov Formation, but the top por-
tocapulus giganteus (Schmidt) (Locs. MK- tion is cut by a fault, and is not exposed in the
3003, 4005; Fig. 17). This species is restricted area.
to the basal part of the zone with the divergentStratigraphy of the Upper Cretaceous System in the Makarov Area 37
Table 3. List of ammonoids, inoceramids and other invertebrates from the Krasnoyarka Formation in the Makarov area.
Species K1 Unit K2 Unit K3 Unit
Ammonoids
Hypophylloceras victriense sp. nov. 4016, 4018
Hypophylloceras cf. nera (Forbes) 4016
Gaudryceras crassicostatum (Jimbo) 2014
Gaudryceras tombetsense Matsumoto 2022, 4014, 4015
Gaudryceras cf. tombetsense Matsumoto 4016
Gaudryceras hamanakense Matsumoto & Yoshida 2023, 4019
Gaudryceras makarovense sp. nov. 2023, 2025, 2029,
2031, 4030
Anagaudryceras seymouriense Macellari 4016
Anagaudryceras matsumotoi Morozumi 2021, 2022, 4014, 2029p
4015, 4016, 4018
Zelandites varuna (Forbes) 3031p
Tetragonites popetensis Yabe 2014 2021, 4014
Saghalinites teshioensis Matsumoto 2014
Pseudophyllites indra (Forbes) 4014, 4015, 4016, 2031
4018
Schlueterella kawadai Matsumoto & Miyauchi 2014
Diplomoceras cf. notabile Whiteaves 4030
Glyptoxoceras sp. 2036
Desmophyllites diphylloides (Forbes) 2014
Canadoceras kossmati Matsumoto 2014, 2015
Canadoceras multicostatum Matsumoto 2014, 4010
Menuites soyaensis (Matsumoto & Miyauchi) 2014, 2017
Pseudomenuites sp. 2014
Pachydiscus gracilis Matsumoto 4017, 4018
Pachydiscus flexuosus Matsumoto 2023 2029, 2031, 2036,
4025, 4028, 4029,
4030, 4032, 4033,
4035
Inoceramids
Sphenoceramus hetonaianus (Matsumoto) 2021, 3029, 4014,
4015, 4016, 4018
Shahmaticeramus shahmati (Salnikova & Zonova) 2021, 4016, 4018
4016, 4018
Shahmaticeramus kusiroensis (Nagao & Matsumoto) 4018
Crustacea
Linuparus sp. 4018 2030, 2036, 4035
K1 Unit Unit consists of greenish gray, intensely bio-
Exposures: Locs. MK2014–2019 along the turbated or mottled muddy sandstone, which
middle course of the Acacia R. (typical sec- contains many large calcareous concretions
tion); middle course of the Victoria R., (Loc. MK2014; Fig. 9). It grades upward into
Rechidtsa R., and Gruzdovka R. greenish gray, dark poorly sorted, coarse,
Thickness: 250–270 m. sandstone interbedded with gray, mottled,
Stratigraphic relationship: The K1 Unit sandy mudstone in the main part of the K1
conformably overlies the B4 Unit of the Bykov Unit (Locs. MK2014–2019). The sandstone
Formation, and conformably underlies the K2 varies in thickness from 50 to 500 cm, and is
Unit. rich in andesitic volcanic rock fragments. Phy-
Lithology: The lowermost part of the K1 cosiphon occurs in the sandy mudstone as well38 Haruyoshi Maeda et al.
as much larger burrows oriented obliquely to Microfossils: No nannofossils were found
the bedding plane. The sandy mudstone also in the K2 Unit.
contains huge (50–100 cm in diameter) spheri- Megafossils: The basal sandstone yields
cal calcareous nodules, some of which are fos- no fossils, but the overlying sandy mudstone is
siliferous. A few vitric tuff beds varying in quite fossiliferous (Table 3). Gaudryceras
thickness from 2 to 5 cm are intercalated in the tombetsense Matsumoto (Figs. 26–31) is the
upper part (Locs. MK2018, 2019). characteristic ammonoid in the lower part of
Microfossils: Cyclagelosphaera sp. and the unit, but Pseudophyllites indra (Forbes)
Watznaueria biporta Bukry occur in samples (Figs. 46–50) and Anagaudryceras matsumotoi
018 and 017, respectively. Morozumi (Fig. 39) are also common in the
Megafossils: Canadoceras multicostatum lower and middle parts. Sphenoceramus heton-
Matsumoto (Fig. 12) is the characteristic am- aianus (Matsumoto) (Fig. 18) is frequently
monoid in the lower part of the K1 Unit, but found in the lower and middle parts. A form of
Tetragonites popetensis Yabe (Fig. 44), Menu- Pachydiscus gracilis Matsumoto (Fig. 14) that
ites soyaensis (Matsumoto and Miyauchi) is much more compressed than the holotype,
(Fig. 13), and Pseudomenuites sp. (Fig. 13) are frequently occurs in the middle part of the
also common (Table 3). Relatively few fossils unit. A lobster (Linuparus sp., Fig. 10) and
were found in the upper part of the K1 Unit. Cidaris sp. are also common in the middle
part. Gaudryceras hamanakense Matsumoto
K2 Unit and Yoshida (Fig. 32) is found in the upper
Exposures: Locs. MK4012–4019 along part. A specimen of Zelandites varuna
the middle course of the Victoria R. (typical (Forbes) (Fig. 38) was obtained from a float
section); middle course of the Acacia R., and calcareous nodule at Loc. MK3031 along the
Gruzdovka R. Gruzovka River. Although the exact horizon
Thickness: 200–500 m. from which the nodule came is uncertain,
Stratigraphic relationship: The K2 Unit judging from the locality and lithology, it al-
conformably overlies the K1 Unit, and con- most without doubt came from the upper part
formably underlies the K3 Unit. o the unit.
Lithology: The lower part of the K2 Unit
consists of gray to light greenish gray, cross- K3 Unit
stratified, coarse to medium grained sandstone. Exposures: Locs. MK2023–2040 along the
Most of the cross-stratification can be classi- middle course of the Acacia R. (typical sec-
fied as trough-type displaying a gentle angle, tion); middle course of the Victoria R., and
while a few beds exhibit features that are char- Gruzdovka R.
acteristic of hummocky cross-stratification Thickness: 400–500 m.
(HCS). Occasionally, the top-most beds of Stratigraphic relationship: The K3 Unit
these structures show current ripples suggest- conformably overlies the K2 Unit, and con-
ing a north to south paleocurrent (Loc. formably underlies the K4a Subunit.
MK4013). A key, widely traceable 30 cm Lithology: The lower part of the K3 Unit
thick, yellowish gray, vitric tuff bed occurs in consists of gray, coarse to medium grained,
the basal part of the unit (Loc. MK4013). bedded sandstone varying in thickness from
The upper part of the K2 Unit becomes fine 50 to 250 cm. Relatively few mudstone inter-
grained and is mainly comprised of dark gray, calations are present in this sandstone. Alter-
intensely bioturbated coarse mudstone, con- nating beds of sandstone and sandy mudstone
taining ellipsoidal calcareous concretions comprise the middle part of the unit. The
20–40 cm in diameter. sandstone beds sometimes show parallel lami-Stratigraphy of the Upper Cretaceous System in the Makarov Area 39
Fig. 9. 1, A distant view of Loc. MK2014 along the Acacia River. The exposure is the Upper Campanian bedded
muddy sandstone of the K1 Unit, Krasnoyarka Formation. 2, A view of Loc. MK2036 along the Acacia River.
Maastrichtian muddy sandstone of the K3 Unit yields many calcareous nodules. The second author (Y.S.) is
shown trying to excavate one of the nodules. 3, A calcareous nodule, found in the river at Loc. MK 2025, con-
taining a 15 cm in diameter specimen of Pachydiscus flexuosus Matsumoto. Specimen deposited in DGMKU.40 Haruyoshi Maeda et al.
Fig. 10. A large calcareous nodule containing Linuparus sp. from the K2 Unit at Loc. MK4018. Note that the an-
tennae and appendages are preserved in situ even though the carapace is crushed. Specimen deposited in
DGMKU. Scale bar5 cm.Stratigraphy of the Upper Cretaceous System in the Makarov Area 41
nations. In the upper part of the unit, dark well-sorted, thus indicating probable deposi-
greenish gray, intensely bioturbated sandstone tion under relatively strong wave action and/
is dominant. Spherical calcareous nodules are or currents. Low-angle cross-stratified, fine
common in the sandy mudstone (Fig. 9). grained sandstones, whose margins converge
In addition, a key, widely traceable, 90 to on the surrounding beds, are dominant in the
120 cm thick, yellowish gray, fine grained, lower part (Loc. MK2044). The distinctive
vitric tuff bed, displaying parallel laminations, features of these beds suggest that they can be
is intercalated in the sandy mudstone (Loc. classified as hummocky cross-stratified sand-
MK2027). stone (HCS) formed by storm events. In the
Microfossils: No nannofossils were found upper part of the unit, medium-grained sand-
in the K3 Unit. stones displaying trough-type cross-stratifica-
Megafossils: Pachydiscus flexuosus Matsu- tion are dominant (Loc. MK2048).
moto (Fig. 15) and Gaudryceras makarovense In the section along the Victoria River, the
Shigeta and Maeda sp. nov. (Figs. 15, 33–37) lithology is highly variable, and many different
are abundant in the middle part of the K3 sediment types are intercalated in the K4a
Unit. An identical assemblage is typically Subunit. These include dark gray sandy mud-
found in the Pugachevo area (see Maeda & stone (Loc. MK4040), a pebble conglomerate
Shigeta, 2005; another article in this volume). bed 10–30 cm thick (Loc. MK4045 etc.), a
P. flexuosus, Glyptoxoceras sp. (Fig. 51), medium-grained sandstone displaying tabu-
Nanonavis sp. and Linuparus sp. occur spo- lar cross-stratification (Loc. MK4046), coal
radically in the upper part of the unit. seams 5–12 cm thick (Loc. MK4048), and
andesitic volcanic breccia 10 m thick (Loc.
K4 Unit MK4042).
The sedimentological features of the K4 Microfossils: No nannofossils were found
Unit, which is the uppermost lithostratigraphic in the K4a Subunit.
unit of the Krasnoyarka Formation, are some- Megafossils: No fossils were found in the
what different from those of the three underly- cross-stratified sandstones. Only rare speci-
ing units. Unlike the lower units of the forma- mens of Nanonavis sp. were found in the
tion, the K4 Unit exhibits a coarsening-upward sandy mudstone in the Victoria section.
sequence, which resembles a deltaic sequence
(Walker & James, 1992). The K4 Unit is sub- K4b Subunit
divided into two distinct subunits, K4a and Exposures: Locs. MK2050–2061 along
K4b, which are described separately. the upper course of the Acacia River (typical
section).
K4a Subunit Thickness: Greater than 450 m.
Exposures: Locs. MK2041–2049 along the Stratigraphic relationship: The K4b Sub-
upper course of the Acacia R. (typical sec- unit conformably overlies the K4a Subunit.
tion); upper course of the Victoria R. The top portion is in fault contact with the
Thickness: 200–500 m. Bykov Formation, which is again exposed
Stratigraphic relationship: The K4a Sub- along the axis of an anticline in the western
unit conformably overlies the K3 Unit, and part of the area.
conformably underlies the K4b Subunit. Lithology: The unit consists mainly of
Lithology: The K4a Subunit consists poorly sorted, mottled, sandy mudstone inter-
mainly of gray to light gray, cross-stratified, calated in thin sandstone beds and beds of vit-
medium to fine grained sandstone. For the ric tuff.
Yezo Group, the sandstone is exceptionally Microfossils: No nannofossils were found42 Haruyoshi Maeda et al.
in the K4b Subunit. schmidti Zone, which is the Lower Campanian
Megafossils: No fossils were found except stage.
allochthonous shell fragments of bivalves Based on the occurrence of nannofossil
which have accumulated as debris in the sand- species Reinhardtites anthophorus, R. levis
stone along with pebbles and patches of shale. and Arkhangelskiella cymbiformis, the B4 Unit
ranges from the Lower to Upper Campanian
stage, which is equivalent to nannofossil zones
Correlation
NC17–20 of Roth (1978), CC17–22 of Siss-
We propose a provisional stratigraphic cor- ingh (1977, 1978) and UC13–15 of Burnett
relation of the Cretaceous deposits in the (1998). Both A. cymbiformis and R. levis have
Makarov area based on the biostratigraphy of their FOs in the Lower Campanian (UC13 and
ammonoids, inoceramids and calcareous nan- UC14, respectively), while R. anthophorus has
nofossils. Then, once all currently ongoing in- its LO in the Upper Campanian (upper bound-
vestigations have been completed, the results ary marker for UC15). According to Burnett
as well as a comprehensive discussion of our (1998), the Campanian–Santonian boundary
conclusions will be published elsewhere. In- occurs slightly below the FO of A. cymbi-
vestigations still in progress include mag- formis (lower boundary marker for UC13).
netostratigraphy, and oxygen and carbon iso- Therefore, the occurrence of A. cymbiformis in
tope stratigraphy. the lower part of the B4 Unit suggests that the
The Cretaceous deposits in the Makarov Campanian–Santonian boundary should lie
area are similar lithologically to those of the within the basal part of the B4 Unit or the
stratotype section in the Naiba area. More upper part of the B3 Unit.
specifically, the Bykov Formation is equivalent The overlying K1 Unit of the Krasnoyarka
to the Upper Yezo Group, while the Krasno- Formation is the Upper Campanian stage as
yarka Formation can be correlated with the indicated by the presence of Canadoceras
Hakobuchi Group in Hokkaido, Japan (Matsu- multicostatum and associated fauna, e.g., Me-
moto, 1942d, 1954; Shigeta et al., 1999; Ko- nuites soyaensis. This assemblage is also
dama et al., 2002). known as the “Soya Fauna” (see Matsumoto &
Based on ammonoid assemblages (Matsu- Miyauchi, 1984). Although one of the diag-
moto, 1942d, 1954, 1959a; Poyarkova, 1987; nostic species, Metaplacenticeras subtilistria-
Zonova et al., 1993; Toshimitsu et al., 1995 tum (Jimbo), has not yet been reported from
etc.), the B1 Unit of the Bykov Formation is Sakhalin, the “Soya Fauna” is widely traceable
supposed to be of Coniacian or Santonian throughout Hokkaido and southern Sakhalin
age, whereas the occurrence of Gaudryceras (Shigeta et al., 1999; Kodama et al., 2002).
tenuiliratum Yabe in the lower and middle part Lower Maastrichtian faunas first appear in
of the B3 Unit indicates that these sediments the K2 Unit. Among these, Sphenoceramus
are of Santonian age. hetonaianus, Gaudryceras tombetsense, and
A change in the fossil assemblage in the Pachydiscus gracilis are also known from the
upper part of the B3 Unit, in which Menuites Hakobuchi Group of Hokkaido (Matsumoto
naumanni and Sphenoceramus orientalis are 1984b; Matsumoto et al., 1979, 1985; Toshim-
common, suggests that this portion of the unit itsu et al., 1995). The K3 Unit frequently
is correlated to the uppermost Santonian or yields Pachydiscus flexuosus and Gaudryceras
lowermost Campanian stage (Matsumoto, makarovense sp. nov., an assemblage that typi-
1959a; Kanie, 1966). The overlying B4 Unit cally can be found in the Pugachevo area,
yields Sphenoceramus schmidti, the index fos- about 50 km south of the Makarov area (see
sil of the widely traceable, 100 m thick S. another paper in this volume). P. flexuosus isStratigraphy of the Upper Cretaceous System in the Makarov Area 43
Fig. 11. Menuites naumanni (Yokoyama) from the B3 Unit, Bykov Formation, along the upper course of the Vic-
toria River. 1–2, NSM PM17268. 3, NSM PM17269. 4, NSM PM17270. Different views of the same speci-
men are linked by the white line (same as in Figs. 12, 13, and 15). Scale bar5 cm.44 Haruyoshi Maeda et al.
Fig. 12. 1–2, Canadoceras kossmati Matsumoto, NSM PM17271, from the uppermost part of the B4 Unit at
Loc. MK4008. 3–4, Canadoceras multicostatum Matsumoto, NSM PM17272, from the basal part of the K1
Unit at Loc. MK2014. Scale bar5 cm.Stratigraphy of the Upper Cretaceous System in the Makarov Area 45
Fig. 13. 1–2, Menuites soyaensis (Matsumoto and Miyauchi), NSM PM17273, from the basal part of the K1 Unit
at Loc. MK2014. 3–5, “Pseudomenuites” sp. from the same locality as Menuites soyaensis. 3, NSM
PM17274. 4–5, NSM PM17275. Scale bar5 cm.46 Haruyoshi Maeda et al.
Fig. 14. Comparison of three Maastrichtian species of Pachydiscus from Sakhalin. 1, 4, Pachydiscus gracilis
Matsumoto, NSM PM17276, from the K2 Unit at Loc. MK4017. 2, 5, Strongly ribbed morphotype of Pachy-
discus flexuosus Matsumoto, NSM PM17277, from the Krasnoyarka Formation at Loc. PC1002 along the Pu-
gachevka River, Pugachevo area (Maeda & Shigeta, 2005). 3, 6, Pachydiscus subcompressus Matsumoto,
DGMKU specimen, from the Krasnoyarka Formation at Loc. NB7024 along the Seim River, Naiba area (this
specimen is figured in Kodama et al., 2002, p. 378, fig. 8H). Note that P. subcompressus has a compressed dis-
coidal shell whose sides are flat and parallel, and fine costae which are independent of the umbilical bullae. P.
flexuosus shows a wide morphological variation. The strongly ribbed morphotype in the middle growth stage
(2, 5) could be mistakenly identified as Canadoceras. Scale bar5 cm.Stratigraphy of the Upper Cretaceous System in the Makarov Area 47
Fig. 15. Upper Maastrichtian ammonoids from the K3 Unit along the Victoria River. 1, 2, 4, 5, Pachydiscus flex-
uosus Matsumoto. 1, NSM PM17278, from Loc. MK4029. 2, DGMKU specimen, from Loc. MK4028. 4–5,
NSM PM17279, from Loc. MK4030. 3, Gaudryceras makarovense Shigeta and Maeda, sp. nov., NSM
PM17206, paratype, from Loc. MK4030. Each scale bar5 cm. Upper scale bar—1, 2, 4 and 5; lower scale
bar—3.48 Haruyoshi Maeda et al.
normally indicative of the lower Upper Maas- & Kanie, 1985) and Urakawa areas (Kanie,
trichtian stage (Matsumoto et al., 1979; 1966). Monotonous mudstone facies, indica-
Toshimitsu et al., 1995), but its stratigraphic tive of a deep offshore environment, predomi-
range is apparently much greater than we for- nate throughout the main part of the group.
merly anticipated. Then, the mudstone facies gradually give way
The geological age of the K4a and K4b sub- to a shallowing-upward sequence in both
units remains uncertain because no direct, age Sakhalin and Hokkaido. Such remarkable sed-
diagnostic evidence has been found. The Sine- imentary continuity and uniformity are charac-
gorsk Fauna, which would apparently suggest teristic of the deposits in the extensive “Yezo
a Danian age (Kalishevich & Posylny, 1958; Basin” (see Shigeta & Maeda, 2005 in this
Kalishevich et al., 1981; Poyarkova, 1987), volume).
was not found during this study. Although slight differences exist at certain
Among the calcareous nannofossils found localities, a regressive deltaic facies finally ap-
in the B3 and B4 units, Repagulum parviden- pears in the uppermost part of the group (ap-
tatum is the most common. The occurrence of prox. the Lower Campanian stage) at many
this normally high latitude index species sug- places in Hokkaido (Matsumoto, 1954;
gests that the B3 and B4 units were deposited Maeda, 1986; Takahashi et al., 2003 etc.).
during Campanian time under the influence of Sedimentation becomes intermittent because
cold water conditions (Crux, 1991). of erosion by strong wave and current action,
and certain fossil zones of the Cam-
panian–Maastrichtian stage are not recorded
Discussion
there.
The significance of the Cretaceous section In contrast, the typical deltaic facies con-
in the Makarov area (Makarov section) can be sisting of a series of coarsening-upward se-
summarized as follows. quences does not appear in the Krasnoyarka
1) A fossiliferous section in the northern Formation except in the uppermost part in
part of southern Sakhalin, ranging in age from southern Sakhalin. In this area, marine sedi-
Santonian to Maastrichtian has been discov- mentation appears to be continuous even in the
ered. regressive phase of Campanian–Maastrichtian
2) A complete succession of the Spheno- age. This facies may be the result of deposi-
ceramus schmidti Zone, which is rarely found tion under a much deeper and quieter environ-
in other areas, is documented. ment than that in Hokkaido. Therefore, strati-
3) The mode of occurrence of a character- graphic and faunal successions are exception-
istic Maastrichtian fossil assemblage repre- ally well preserved in southern Sakhalin (Mat-
sented by Pachydiscus flexuosus is document- sumoto, 1942d, 1954; Poyarkova, 1987; Shige-
ed. ta et al., 1999; Kodama et al., 2002).
The lithology of the Cretaceous strata in the
The Position of the Makarov section in the Makarov area is similar in detail to that of the
“Yezo Basin” type section in the Naiba area (Poyarkova,
The sedimentary features of the Cretaceous 1987; Kodama et al., 2002). For example, in
Yezo Group (Supergroup) are similar the Naiba section the lithological transition
throughout southern Sakhalin and the eastern from the Bykov Formation to the overlying
central zone of Hokkaido: e.g., Wakkanai Krasnoyarka Formation is identical to that in
(Matsumoto & Miyauchi, 1984), Nakaton- the Makarov section located 200 km to the
betsu (Matsumoto et al., 1980; Ando et al., north. The succession consists of, in ascending
2001), Hidaka (Obata et al., 1973; Kawaguchi order: 1) massive mudstone, 2) greenish gray,Stratigraphy of the Upper Cretaceous System in the Makarov Area 49
Fig. 16. 1, Sphenoceramus nagaoi (Matsumoto and Ueda), NSM PM17280, from the B3 Unit at Loc. MK2008,
1.0. 2, Anisomyon cassidarius (Yokoyama), NSM PM17281, from the B3 Unit at Loc. MK2008, 1.0. 3,
“Gigantocaplus” transformis (Dundo), NSM PM17282, from the uppermost part of the B3 Unit at Loc.
MK2062, 1.0. 4–5, Sphenoceramus orientalis (Sokolov), from the uppermost part of the B3 Unit at Loc.
MK2062. 4, NSM PM17283, 1.0. 5, NSM PM17284, 1.0.50 Haruyoshi Maeda et al.
Fig. 17. 1, 2, 4, Sphenoceramus schmidti (Michael), from the B4 Unit at Loc. MK2009. 1, NSM PM17285, from
the upper part of the S. schmidti Zone, 0.4. 2, NSM PM17286, from the upper part of the S. schmidti Zone,
0.4. 4, NSM PM17288, from the basal part of the S. schmidti Zone, 0.4. 3, Gigantocaplus giganteus
(Schmidt), NSM PM17287, from the basal part of the B4 Unit (basal part of the S. schmidti Zone ) at Loc.
MK2009, 0.4.Stratigraphy of the Upper Cretaceous System in the Makarov Area 51
Fig. 18. 1–3, Sphenoceramus schmidti (Michael), from the basal part of the B4 Unit at Loc. MK2009. 1, NSM
PM17289, 1.0. 2, NSM PM17290, 1.0. 3, NSM PM17291, 1.0. 4–6, Sphenoceramus hetonaianus (Ma-
tsumoto), from the K2 Unit at Loc. MK2021. 4, NSM PM17292, 1.0. 5, NSM PM17293, 1.0. 6, NSM
PM17294, 1.0. 7–12, Shahmaticeramus shahmati (Salnikova and Zonova) from the K2 Unit. 7, NSM
PM17295 from Loc. MK2021, 1.0. 8, NSM PM17296 from Loc. MK2021, 1.0. 9. NSM PM17297 from
Loc. MK4016, 1.0. 10. NSM PM17298 from Loc. MK4018, 1.0. 11. NSM PM17299 from Loc. MK4018,
1.0. 12. NSM PM17300 from Loc. MK4018, 1.0. 13, 14, Shahmaticeramus kusiroensis (Nagao and
Matsumoto) from the K2 Unit at Loc. MK4018. 13, NSM PM17301, 1.0. 14, NSM PM17302, 1.0.52 Haruyoshi Maeda et al.
mottled muddy sandstone containing many in nearly all sections in Hokkaido and south-
calcareous nodules, 3) dark greenish-gray, ern Sakhalin because of an increasing influx of
poorly sorted, bedded coarse sandstone com- sands during the regressive phase (discussed
posed of andesitic volcaniclasts, and 4) alter- above). The FAD of S. schmidti, or the basal
nating beds of greenish gray sandstone and part of the S. schmidti Zone, is observable in
sandy mudstone in an upward sequence. One various sections. However, the LAD of S.
of the remarkable characteristics of the Yezo schmidti, or upper part of the S. schmidti Zone,
Group is its uniformity and continuity of litho- is rarely preserved. The top part is not clearly
facies and biofacies, extending over a distance recognizable, even in the Naiba section. Our
of 200 km or more along an active plate mar- studies reveal that in most cases, the so-called
gin. “S. schmidti Zone” discussed in various litera-
However, in spite of the lithological similar- ture, actually represents only the basal part of
ity of the Cretaceous System throughout the zone.
southern Sakhalin, it is obvious that the datum In contrast, the Makarov section is a rare ex-
planes of a few fossil zones extend across ample in which a complete, 100 m thick, suc-
some lithostratigraphic boundaries. For exam- cession of the S. schmidti Zone is preserved
ple, in the Naiba section, the Lower Campan- (Figs. 5, 6, 19). In the basal part of the S.
ian Sphenoceramus schmidti Zone is interca- schmidti Zone, the morphotype possessing di-
lated in the basal part of the Krasnoyarka For- agnostic divergent ribs in the adult stage is
mation (Matsumoto, 1942d; Zakharov et al., abundant. At this level, Gigantocapulus gigan-
1984; Poyarkova, 1987; Kodama et al., 2002). teus is closely associated with this particular
On the other hand, in the Makarov section, the morphotype (Fig. 17; Locs. MK3003, 4005).
S. schmidti Zone exists within the sandy mud- This association of S. schmidti and G. gigan-
stone of the B4 Unit of the Bykov Formation. teus has led us to, hypothesize that the two
More specifically, in the Makarov area, the species lived in a symbiotic relationship, with
FAD of S. schmidti is about 150 m below the the latter species attached to the shell-surface
base of the Krasnoyarka Formation (Figs. 5, of the former (Hayami & Kanie, 1980). This
6). These features aptly demonstrate the im- hypothesis still appears to be valid, and our
portant problems inherent with chronological observations reveal the following two points,
correlation between lithofacies and biofacies. which will be utilized to test the principle in
further studies.
A Complete succession of the Sphenocera- 1) G. giganteus only occurs in the basal
mus schmidti Zone part of the zone in association with the mor-
Sphenoceramus schmidti is a well known photype possessing divergent ribbing. G. gi-
and a long established fossil taxon within the ganteus completely disappears above the basal
Yezo Group. It usually occurs in traceable part of the S. schmidti Zone (Fig. 19).
shellbeds which represent the S. schmidti 2) Without exception, G. giganteus attach-
Zone. Many workers have been interested in es itself to the lower valve of S. schmidti, and
the various aspects of this species because of is always in the upside down position.
its abundant occurrence and peculiar morphol- In the upper part of the S. schmidti Zone,
ogy of divergent ribs, e.g., biostratigraphy smooth morphotypes, in which the divergent
(Pergament, 1974), taxonomy (Zonova, 1987; ribs appear only in the early growth stage, be-
Zonova et al., 1993; Tashiro et al., 1995), and come dominant (Figs. 17, 19; discussed later).
paleoecology (Hayami & Kanie, 1980; Tashiro Several morphotypes, including the smooth
et al., 1995). type, were needlessly divided into several
However, the S. schmidti Zone is incomplete species by some authors (Pergament, 1974;Stratigraphy of the Upper Cretaceous System in the Makarov Area 53
Fig. 19. Columnar section showing detailed occurrences of key species of the Sphenoceramus schmidti Zone in
the B4 Unit of the Bykov Formation along the Victoria River. A complete succession of the S. schmidti Zone
is well observable. Solid circle: occurrence of morphotype possessing divergent ribs in adult shells; open cir-
cle: morphotype possessing smooth adult shells. Note that Gigantocapulus giganteus (solid triangle) is associ-
ated only with the former morphotype, and occurs restrictedly from the basal part of the S. schmidti Zone.54 Haruyoshi Maeda et al.
Zonova, 1987; Zonova et al., 1993). However, the Krasnoyarka Formation in the Naiba and
it is now known that S. schmidti exhibits Sinegorsk areas (Fig. 14; Matsumoto, 1942d,
a very wide range of morphological varia- 1954; Kodama et al., 2002, table 3, fig. 8).
tion. The successive change of morphotypes However, it is not found in the Makarov area,
shown in Fig. 19 can also be explained by even though several specimens mistakenly
heterochrony within a single evolutional identified as P. subcompressus have been listed
biospecies, i.e., the timing of the appearance in various papers.
of divergent ribs has been ontogenetically ac- P. subcompressus is clearly distinguishable
celerated. Therefore, we herein include all of morphologically from P. flexuosus and its re-
the morphotypes within the synonymy of S. lated species. P. subcompressus has very com-
schmidti. pressed whorls, whose flanks are nearly flat,
The discovery of a complete succession of and shell ornamentation is clearly distin-
the S. schmidti Zone in the Makarov area is guished by umbilical bullae and short, sepa-
very important for further research. Further- rate ventrolateral ribs (Fig. 14). These features
more, Japanese workers must be mindful that a closely resemble those of the European type
complete succession of the S. schmidti Zone species, P. neubergicus (Hauer) and the Indian
does not exist on Hokkaido. For this reason, species: P. compressus Spath (Kossmat,
we attach even greater importance to the 1895–1898).
Makarov section. Failure to recognize that the In the Naiba section, P. subcompressus is
S. schmidti Zone in Hokkaido consists of only usually associated with Zelandites varuna, an-
partial successions, will merely lead to false other important element of the Indian Maas-
assumptions and conclusions about the zone. trichtian fauna (Kodama et al., 2002, fig. 8).
This volume of evidence suggests that P. sub-
Aspects of the Maastrichtian faunas compressus is not indigenous to the North Pa-
The Maastrichtian assemblages in the cific Realm, but is actually a “foreign species”,
Makarov area, which consist of Pachydiscus, which migrated northward from the Indian
Gaudryceras, Linuparus, and Cidaris, resem- province.
ble those in the Pugachevo, Manui, and
Kril’on areas in southern Sakhalin (Zonova et Systematic Paleontology
al., 1993; Yazikova, 1994; Shigeta et al., 1999) (By Y. Shigeta and H. Maeda)
and the Nakatonbetsu and Hobetsu areas in
Abbreviations: Dshell diameter; Uum-
Hokkaido (Matsumoto et al., 1979, 1980;
bilical diameter; Hwhorl height; Bwhorl
Ando et al., 2001). The faunal contents are
width.
also similar to those of the Izumi Group in
southwest Japan (Matsumoto & Morozumi,
Suborder Phylloceratina Arkell, 1950
1980; Morozumi, 1985). Among the various
pachydiscid species, P. flexuosus (Fig. 15) fre- Superfamily Phylloceratoidea Zittel, 1884
quently occurs in the Makarov area. Our ob-
Family Phylloceratidae Zittel, 1884
servations reveal that P. flexuosus is widely
distributed in Maastrichtian successions Genus Hypophylloceras Salfeld, 1924
throughout southern Sakhalin and Hokkaido.
Subgenus Neophylloceras Shimizu, 1934
P. flexuosus may be indigenous to the North
Pacific Realm, and it has several related Type species: Ammonites (Scaphites?) ramo-
species. sus Meek, 1857.
In contrast, the well-known species Pachy- Remarks: Neophylloceras was established
discus subcompressus Matsumoto occurs in by Shimizu (1934, p. 61 in Shimizu andStratigraphy of the Upper Cretaceous System in the Makarov Area 55
Obata), and has been regarded as either within lel flanks and rounded venter, with the greatest
the synonymy of Hypophylloceras, as a sub- width occurring at mid-flank. The umbilicus is
genus of Hypophylloceras or Phylloceras, or narrow with a very steep wall and abruptly
an independent genus. We herein follow rounded shoulder. On later whorls the lirae
Wright et al. (1996) and treat Neophylloceras gradually become distant, barely raised ribs,
as a subgenus of Hypophylloceras. while the internal mold becomes almost
smooth. The suture is barely visible, but obvi-
ously consists of numerous deeply incised ele-
Hypophylloceras (Neophylloceras)
ments with phylloid terminals.
victriense sp. nov.
Comparison: Hypophylloceras (Neophyllo-
Figs. 20–23
ceras) victriense sp. nov. closely resembles
Type: Holotype, NSM PM17171, is from some Maastrichtian species of Hypophyllo-
Loc. MK4018 along the Victoria River, and ceras such as H. (N.) nera (Forbes, 1846, p.
consists mostly of the phragmocone of a large 106), H. (N.) surya (Forbes, 1846, p. 106) and
shell. H. (N.) groelandicum (Birkelund, 1965, p. 23),
Material (Paratypes): Three specimens, but it is distinguished from the latter by having
NSM PM17172–17174, from Loc. MK4016, very weak lirae or a nearly smooth shell sur-
and three specimens, NSM PM17175–17177, face at middle to later growth stages.
from Loc. MK4018 along the Victoria River. Etymology: This species is named for the
Diagnosis: Very involute, large-sized Neo- Victoria River, which is the type locality.
phylloceras with compressed whorl section Occurrence: The described specimens were
and nearly smooth or very weak ribs on later collected from a bed in which Sphenoceramus
whorls. Suture is as for Neophylloceras. hetonaianus and Shahmaticeramus kushiroen-
Dimensions: See Table 4. sis occur, in the K2 Unit of the Krasnoyarka
Description: Early whorls (up to 20 mm in Formation in the Makarov area, Sakhalin. This
diameter). Involute shell characterized by a level is upper Lower to lower Upper Maas-
very narrow umbilicus with a very steep um- trichtian.
bilical wall, and a compressed oval whorl sec-
tion with gently rounded flanks and rounded Hypophylloceras (Neophylloceras)
venter, with the greatest width occurring at cf. nera (Forbes, 1846)
mid-flank. Ornamentation consists of fine, Fig. 24.1–24.4
dense, lirae, which arise at the umbilical seam, cf. Ammonites Nera Forbes, 1846, p. 106, pl. 8, fig. 7.
sweep gently forward across the inner flank, cf. Phylloceras nera (Forbes). Kossmat, 1895, p. 109, 160,
and then pass straight across the mid-flank and pl. 16, fig. 2.
venter. cf. Phylloceras (Neophylloceras) nera (Forbes). Kennedy
Middle and later whorls (over 20 mm in di- and Henderson, 1992, p. 389, pl. 1, figs. 10–12, pl. 15,
figs. 1–2, text-fig. 3A; Matsumoto and Toshimitsu,
ameter). As size increases, the whorl section
1996, p. 3, pls. 1–2.
becomes more compressed, with nearly paral-
Tabe 4. Measurements (in mm) of Hypophylloceras victriense Shigeta and Maeda sp. nov. at the last preserved septum.
Specimen D U H B U/D B/H
NSM PM17171 147.7 8.4 83.8 36.0 0.06 0.43
NSM PM17176 93.0 6.5 52.4 23.8 0.07 0.45
NSM PM17175 74.1 4.6 43.1 19.7 0.06 0.46
NSM PM17173 50.0 3.3 29.2 15.0 0.07 0.5156 Haruyoshi Maeda et al.
Fig. 20. Hypophylloceras (Neophylloceras) victriense Shigeta and Maeda, sp. nov. 1–4, NSM PM17171, holo-
type, from Loc. MK4018. Scale bar5 cm.Stratigraphy of the Upper Cretaceous System in the Makarov Area 57
Fig. 21. Hypophylloceras (Neophylloceras) victriense Shigeta and Maeda, sp. nov. 1–2, NSM PM17172,
paratype, from Loc. MK4016, 1.0. 3–4, NSM PM17173, paratype, from Loc. MK4016, 1.0. 5–7, NSM
PM17174, paratype, from Loc. MK4016, 1.0. 8–10, NSM PM17175, paratype, from Loc. MK4018, 1.0.58 Haruyoshi Maeda et al.
Fig. 22. Hypophylloceras (Neophylloceras) victriense Shigeta and Maeda, sp. nov. 1–4, NSM PM17176,
paratype, from Loc. MK4018, 1.0.Stratigraphy of the Upper Cretaceous System in the Makarov Area
Fig. 23. Hypophylloceras (Neophylloceras) victriense Shigeta and Maeda, sp. nov. 1–3, NSM PM17177, paratype, from Loc. MK4018, 0.7.
5960 Haruyoshi Maeda et al.
Material: Two specimens, NSM PM17178, Phyllopachyceras ezoense (Yokoyama, 1890)
17179, from Loc. MK4016 along the Victoria Fig. 24.5–24.11
River. Phylloceras ezoense Yokoyama, 1890, p. 178, pl. 19, fig.
Description: Very involute shell distin- 2; Yabe and Shimizu, 1921, p. 54, pl. 8, fig. 2.
guished by a compressed oval whorl section Phyllopachyceras ezoense (Yokoyama). Matsumoto,
with nearly parallel flanks and rounded venter, 1942c, p. 674; Matsumoto and Obata, 1955, pl. 30, fig.
with the greatest width occurring at mid-flank. 3; Matsumoto and Miyauchi, 1984, p. 38, pl. 10, figs.
3–4; Alabushev and Wiedmann, 1997, p. 6, pl. 1, figs.
The umbilicus is narrow with a very steep wall
3–5.
and rounded shoulder. Ornamentation consists
of fine, dense lirae, which arise at the umbili- Type: Repository of the holotype (Yokoya-
cal seam, sweep gently forward across the ma, 1890, p. 178, pl. 19, fig. 2), from the Yezo
inner flank, and then pass straight across mid- Group in the Urakawa area, south central
flanks to the venter. Flanks of inner whorls are Hokkaido, is the Bavarian State Collection of
ornamented by broad undulations. Palaeontology and Geology in Munich, Ger-
Although the suture is not completely ex- many. Its exact collection locality and horizon
posed on the present specimens, the visible are unknown.
portions are deeply incised and finely divided. Material: Two specimens, NSM PM17180,
Discussion: Hypophylloceras (Neophyllo- 17181, from Loc. MK2062 along the Acacia
ceras) nera was established for a small, appar- River. NSM PM17182, from Loc. MK2015
ently immature specimen from the Maastricht- along the Acacia River.
ian of southern India. However, Matsumoto Description: Very involute shell, charac-
and Toshimitsu (1996) provided a revised di- terized by a very narrow, deep, funnel-shaped
agnosis for the species based on three larger umbilicus and a slightly inflated, sub-circular
specimens and a smaller one collected from whorl section with a moderately arched venter.
the Sphenoceramus hetonaianus-Pachydiscus The greatest width occurs at mid-flank. Orna-
gracilis Zone (upper Lower Maastrichtian) in mentation consists of dense, very fine prorsira-
the Hobetsu area, central Hokkaido. Conse- diate lirae that cross the flanks and then be-
quently, the distinctive features of the present come slightly sinuous on the ventrolateral
specimens enable us to identify them with rea- shoulders, before crossing the venter in a
sonable confidence as H. (N.) nera. broad convex arch. Mature whorls are orna-
Occurrence: The described specimens were mented by frequent, strong, rounded, prorsira-
found in the same bed in which Sphenocera- diate ribs which originate low on the flank and
mus hetonaianus occurs in the K2 Unit of the cross the venter in a moderately broad convex
Krasnoyarka Formation in the Makarov area, arch. The suture line is not exposed.
Sakhalin. This level is upper Lower to lower Occurrence: The described specimens were
Upper Maastrichtian. collected in the Sphenoceramus orientalis and
Canadoceras kossmati bearing beds in the B3
Genus Phyllopachyceras Spath, 1925 and B4 units of the Bykov Formation, in the
Makarov area, Sakhalin. These levels are
Type species: Ammonites infundibulum equivalent to the upper Lower Campanian, but
d’Orbigny 1841. the species is abundant in beds of Turonian to
Campanian age in Hokkaido and Sakhalin
(Toshimitsu & Hirano, 2000).You can also read
